Ezra and coworkers are studying the internal and reactive dynamics of small polyatomic molecules. One aim of the project is to develop theoretical methods for characterization of highly excited vibrational states of molecules, for which conventional approaches are of limited use. The results of this research will help interpret high-resolution rotation-vibration spectra and elucidate the relation between classical mechanical (Newton) and quantum (Schroedinger) descriptions of atomic motions in molecules. Ezra and coworkers are currently investigating the light-induced fragmentation of the hydrogen peroxide molecule using classical trajectories. Of particular interest is the sensitivity of theoretical predictions for the fragmentation rate, for example, to details of the model potential surface. The GAUSSIAN electronic structure codes are being used to make ab initio computations of dynamically significant regions of the potential energy surface.